Onsemi C106M1G Silicon Controlled Rectifier: Technical Specifications and Application Circuits
The ON Semiconductor C106M1G is a classic, industry-standard Silicon Controlled Rectifier (SCR) designed for a wide range of AC power control and switching applications. As a member of the sensitive gate SCR family, it is characterized by its very low gate triggering current, making it highly efficient and easy to drive with low-power control circuits. This article delves into its key technical specifications and presents common application circuits.
Technical Specifications
The C106M1G is a plastic-packaged SCR (TO-225AA) with a standard pinout: Anode, Cathode, and Gate. Its defining electrical characteristics include:
Repetitive Peak Off-State Voltage (VDRM): 400 V. This is the maximum forward voltage the SCR can block repeatedly. This rating makes it suitable for a wide range of line-voltage applications, including 120VAC and 240VAC systems.
On-State Current (IT(RMS)): 4 A RMS. This specifies the maximum continuous RMS current the device can conduct in the on-state.
Gate Trigger Current (IGT): 200 µA (max). This is a critical parameter, indicating the extremely sensitive gate of this SCR. Such a low triggering current allows it to be driven directly from high-impedance sources like logic gates, timers (e.g., 555), or microcontrollers with only a small series resistor.
Gate Trigger Voltage (VGT): 0.8 V (max). The maximum voltage required between gate and cathode to trigger the device into conduction.
Holding Current (IH): 5 mA (max). The minimum anode current required to keep the SCR in the on-state after the gate trigger has been removed.
Application Circuits
The C106M1G's high sensitivity and robust voltage rating make it ideal for numerous power control scenarios.
1. Half-Wave AC Power Control (Light Dimmer / Motor Speed Control)
This is a fundamental circuit. An RC phase-shift network controls the timing at which a Diac (e.g., DB3) breaks over and delivers a current pulse to the gate of the SCR. By adjusting the resistor (R), the firing angle is varied, which in turn controls the amount of power delivered to the load (e.g., a lamp or universal motor) during each half-cycle of AC power.
2. DC Latch / Crowbar Over-Voltage Protection
In this critical safety circuit, the SCR is placed across the power supply output. A Zener diode is configured to begin conducting when the supply voltage exceeds a predetermined safe level. This current then triggers the sensitive gate of the C106M1G, causing it to latch on and create a short circuit (crowbar) across the output. This action will blow a fuse or trip a circuit breaker, protecting the connected load from damaging over-voltage conditions.
3. Microcontroller-Interfaced Relay Driver
The low IGT of the C106M1G allows it to be driven directly from a microcontroller's output pin. A small series resistor (e.g., 100Ω) is placed between the MCU pin and the SCR's gate. A pulse from the MCU triggers the SCR, which then switches a larger DC current to energize a relay coil. A "flyback" diode must be placed in reverse bias across the relay coil to protect the SCR from voltage spikes generated when the coil is de-energized.
The Onsemi C106M1G remains a highly versatile and cost-effective solution for medium-power switching. Its exceptional gate sensitivity is its standout feature, simplifying driver circuit design and enabling direct control from low-power logic. While suitable for various applications, designers must pay close attention to snubber circuits for inductive loads and proper heat sinking when operating near its maximum current ratings to ensure long-term reliability.
Keywords: Silicon Controlled Rectifier, Sensitive Gate, AC Power Control, Over-Voltage Protection, Crowbar Circuit
